1. Field of the Invention
The present invention relates to the field of computer networks, and in particular to a method and apparatus for desirable network components.
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2. Background Art
Computer network systems make use of one or more network components, such as storage devices. The network components are coupled to the computer network and are configured to communicate using the network protocol of the computer network. Some network protocols use connectors and cables for coupling to the network which are desirable for some purpose while other network protocols use connectors and cables for coupling to the network which are less desirable for that same purpose. Measures of desirability include cost, durability and size. Other measures of desirability also exist. Which measure of desirability is applied in a particular design depends on the goals of the design.
Users and manufacturers of the network protocols which use less desirable connectors and cables desire to improve the desirability of the computer network without changing the network protocol. This problem can be better understood by a review of computer networks.
Computer Networks
Computer networks are groups of computers and computer components in which the computers and components are interconnected via computer cables, infrared light signals, or low-power radiowave transmissions over short distances to form local area networks (LANs) or via telephone lines, television cables, or satellite links to form wide-area networks (WANs). FIG. 1 illustrates one embodiment of a computer network. Terminals 1 (100), 2 (110) and 3 (120) are coupled with storage devices 1 (130) and 2 (140) via an interconnect (150).
Network Protocols
Once computers and computer components are interconnected, network protocols are used to allow computers and computer components to interpret the signals they receive from other members of the network. Network protocols are standardized rules for the format and exchange of messages that the end points in a network connection use to send signals between each other. Both end points must recognize and observe the protocol. Protocols are often described in an industry or international standard.
Network protocols also include flow control, which keeps a data sender from swamping a receiver with messages it has no time to process or space to store, and error control, which involves error detection and automatic resending of messages to compensate for errors in transmission.
The standardization of protocols is an international effort. Since it would otherwise be impossible for different kinds of machines running diverse operating systems to communicate with one another, the key concern has been that system components (computers) be “open” (i.e., open for communication with other open components). This terminology comes from the open systems interconnection (OSI) communication standards, established by the International Organization for Standardization. The OSI reference model specifies protocol standards in seven layers.
FIG. 2 illustrates the seven layers for network protocol in accordance with OSI standards. The layers, from lowest to highest, are the physical layer (200), the datalink layer (210), the network layer (220), the transport layer (230), the session layer (240), the presentation layer (250) and the application layer (260).
The layering provides a modularization of the protocols and hence of their implementations. Each layer is defined by the functions it relies upon from the next lower level and by the services it provides to the layer above it. At the lowest level, the physical layer, rules for the transport of bits across a physical link are defined. Next, the data-link layer handles standard-size packets of data bits and adds reliability in the form of error detection and flow control.
Network and transport layers (often combined in implementations) break up messages into the standard-size packets and route them to their destinations. The session layer supports interactions between application processes on two hosts (machines). For example, it provides a mechanism with which to insert checkpoints (saving the current status of a task) into a long file transfer so that, in case of a failure, only the data after the last checkpoint need to be retransmitted. The presentation layer is concerned with such functions as transformation of data encodings, so that heterogeneous systems may engage in meaningful communication.
At the highest, or application, layer are protocols that support specific applications. An example of such an application is the transfer of files from one host to another. Another application allows a user working at any kind of terminal or workstation to access any host as if the user were local.
Fibre Channel
Fibre Channel (FC) is an industry-standard, high-speed network protocol. The FC standard supports bandwidths of 133 Megabits per second (Mb/sec.), 266 Mb/sec., 532 Mb/sec., 1.0625 Gigabits per second (Gb/sec.), and 4 Gb/sec. (proposed) at distances of up to ten kilometers. Gigabit Fibre Channel's maximum data rate is 100 Megabytes per second (MB/sec.) (200 MB/sec. full-duplex) after accounting for overhead.
In addition to its strong channel characteristics, Fibre Channel provides powerful networking capabilities, allowing switches and hubs to enable the interconnection of systems and storage into tightly-knit clusters. These clusters are capable of providing high levels of performance for file service, database management, or general purpose computing. Because it is able to span up to 10 kilometers between nodes, Fibre Channel allows the very high speed movement of data between systems that are greatly separated from one another.
FC is also a high-reliability interconnect. The interface is robust enough to allow multiple devices to be removed from the loop at one time with no interruption in data transfer. In addition, the interface attaches sophisticated error detecting codes to each packet of user data. These codes are check by the receiver of the data, which request a re-send if there is any discrepancy. However, electronic components used with FC devices are more expensive than electronic components used with other network protocol devices.
FIG. 3 illustrates a Fibre Channel network component. The component (300) contains a Fibre Channel compliant connector (310) which couples to a Fibre Channel compliant cable (320). The connector and cable both operate at the physical layer of the Fibre Channel network protocol.
Gigabit Ethernet
Gigabit Ethernet is a local area network (LAN) transmission standard that provides a data rate of 1 billion bits per second (one gigabit). Gigabit Ethernet is defined in the IEEE 802.3 standard and is used as an enterprise backbone. Gigabit Ethernet is carried primarily on optical fiber (with very short distances possible on copper media). Existing Ethernet LANs with 10 and 100 Mb/sec. cards can feed into a Gigabit Ethernet backbone. For example, Gigabit Ethernet devices can use CAT-5 twisted pair cables with RJ-45 connectors.
CAT-5 is one of several categories of standards defined by the American National Standards Institute/Electronic Industries Association (ANSI/EIA) Standard 568. The standards categories specify twisted pair cabling systems (wires, junctions, and connectors) in terms of the data rates that the systems can sustain. The specifications describe the cable material as well as the types of connectors and junction blocks to be used in order to conform to a category.
CAT-5 is the category incorporated into the Gigabit Ethernet specification for short distance wiring. While longer connections using Gigabit Ethernet use fiber optic cables. The CAT-5 wiring is already in place in many network systems for the final connection to desktop network components. Thus, Gigabit Ethernet is less expensive to install in such network systems.
Electronic components used in Gigabit Ethernet devices are less expensive than electronic components used for the same function in Fibre Channel devices. Additionally, the physical layer of Gigabit Ethernet is identical to the physical layer of Fibre Channel.
FIG. 4 illustrates a Gigabit Ethernet network component. The component (400) contains a Gigabit Ethernet compliant connector (410) which couples to a Gigabit Ethernet compliant cable (420). The connector and cable both operate at the physical layer of the Gigabit Ethernet network protocol.